The present invention relates to a method for forming insulating film between interconnect layers in microelectronic devices. More specifically, the present invention relates to a method for forming insulating film between interconnect layers in microelectronic devices by using siloxane-based resins prepared from siloxane monomers having cyclic structure.
Feature size in the microelectronic device has to be reduced because circuit density in multilevel integrated circuit devices is increasing. But, there are fatal problems such as R(resistance)xc3x97C(capacitance) delay due to crosstalk between interconnect lines. Therefore, dielectric constant of the interlayer insulating film should be lowered so as to decrease RC delay as much as possible. For this purpose, there have been various attempts to use materials with low dielectric constant in the insulating film. For example, hydrogensilsesquioxane having a dielectric constant of approximately 3.1 has replaced SiO2 in chemical vapor deposition(CVD). The hydrogensilsesquioxane can be also applied to spin-coating due to its excellent planation property. Hydrogensilsesquioxane resins as well as preparing method thereof are well known in the art. For example, U.S. Pat. No. 3,615,272 discloses a method for preparing completely condensed soluble hydrogensilsesquioxane resins, which comprises the steps of condensing trichlorosilanes in a sulfuric acid medium, and then washing the resulting resins with D.I.-water or aqueous sulfuric acid. Further, U.S. Pat. No. 5,010,159 discloses a method for synthesizing soluble condensed hydridosilicon resins, which comprises the steps of hydrolyzing hydridosilanes in an arylsulfuric acid hydrate-containing hydrolysis medium, and then contacting the resulting resins with a neutralizing agent.
However, the previous resins have not provided sufficiently low dielectric constant required for in microelectronic devices.
A feature of the present invention is a method for forming low dielectric insulating film between interconnect layers in microelectronic devices by using siloxane-based resins prepared from siloxane monomers having cyclic structure.
Another feature of the present invention is the siloxane-based resins prepared from siloxane monomers having cyclic structure.
In accordance with one aspect of the present invention, there is provided a method for forming low dielectric insulating film between interconnect layers in microelectronic devices, said method comprising the steps of: preparing siloxane-based resins by hydrolyzing and polycondensing the compound represented by the following formula (1), with or without the compound represented by the following formula (2), in an organic solvent in the presence of a catalyst and water; coating a silicon substrate with the siloxane-based resins dissolved in an organic solvent; and heat-curing the resulting coating film: xe2x80x83RSiX1X2X3xe2x80x83xe2x80x83[2]
In the above formulas (1) and (2),
R is hydrogen atom, C1xcx9cC3 alkyl group, C3xcx9cC10 cycloalkyl group, or C6xcx9cC15 aryl group;
X1, X2 and X3 are independently C1xcx9cC3 alkyl group, C1xcx9cC10 alkoxy group, or halogen atom;
n is an integer ranging from 3 to 8; and
m is an integer ranging from 1 to 10.
In accordance with another aspect of the present invention, there is provided the siloxane-based resins prepared by hydrolyzing and polycondensing the compound represented by the above formula (1), with or without the compound represented by the above formula (2), in an organic solvent in the presence of a catalyst and water.
All of the above features and other features of the present invention will be successfully achieved from the present invention described in the following.
The Priority Korean Patent Application No. 2000-71645 filed on Nov. 29, 2000 is hereby incorporated in its entirety by reference.
According to the present invention, there is provided a method for forming interlayer insulating film between interconnect layers in microelectronic devices by using novel soluble cyclic siloxane-based resins having a dielectric constant less than 3.0. This method comprises the steps of: preparing siloxane-based resins by hydrolyzing and polycondensing only siloxane monomers, or both siloxane monomers and silane-based monomers in the presence of a catalyst; coating a silicon substrate with the siloxane-based resins dissolved in an organic solvent; and heating the coated substrate to cure the siloxane-based resins. The thin film thus formed has a dielectric constant less than 3.0, preferably 2.0xcx9c2.7, and therefore, it is useful for low dielectric coating film between interconnect layers in microelectronic devices.
In the present invention, the cyclic siloxane monomers can be represented by the following formula (1): 
In the above formula (1),
R is hydrogen atom, C1xcx9cC3 alkyl group, C3xcx9cC10 cycloalkyl group, or C6xcx9cC15 aryl group;
X1, X2 and X3 are independently C1xcx9cC3 alkyl group, C1xcx9cC10 alkoxy group, or halogen atom;
n is an integer ranging from 3 to 8; and
m is an integer ranging from 1 to 10.
As can be seen from the above formula (1), silicon atoms are linked to each other through oxygen atoms to form cyclic structure, and the end of each branch comprises organic groups constituting a hydrolyzable substituent.
The method for preparing the cyclic siloxane monomers is not specifically limited, but hydrosililation using a metal catalyst is preferred.
The siloxane-based resins used in the present invention can be prepared by hydrolyzing and polycondensing siloxane monomers of the above formula (1), with or without silane-based monomers of the following formula (2), in the presence of an appropriate catalyst:
RSiX1X2X3xe2x80x83xe2x80x83[21]
In the above formula (2),
R is hydrogen atom, C1xcx9cC3 alkyl group, C3xcx9cC10 cycloalkyl group, or C6xcx9cC15 aryl group; and
X1, X2 and X3 are independently C1xcx9cC3 alkyl group, C1xcx9cC10 alkoxy group, or halogen atom.
The catalyst used in the preparation of the siloxane-based resins is not specifically limited, but preferably hydrochloric acid, benzenesulfonic acid, oxalic acid, formic acid, potassium hydroxide, sodium hydroxide, triethylamine, sodium bicarbonate, or pyridine.
In the hydrolysis and polycondensation reaction, water is added at 1.0xcx9c100.0 equivalents, preferably 1.0xcx9c10.0 equivalents per one equivalent of reactive groups in the monomers, and the catalyst is added at 0.00001xcx9c10 equivalents, preferably 0.0001xcx9c5 equivalents per one equivalent of reactive groups in the monomers, and then the reaction is carried out at 0xcx9c200xc2x0 C., preferably 50xcx9c110xc2x0 C. for 1xcx9c100 hrs, preferably 5xcx9c48 hrs. In addition, the organic solvent used in this reaction is preferably aromatic hydrocarbon solvent, aliphatic hydrocarbon solvent, ketone-based solvent, ether-based solvent, acetate-based solvent, alcohol-based solvent, silicon-based solvent, or mixtures thereof.
The siloxane-based resins thus prepared may be dissolved in a suitable organic solvent for further use. Examples of this solvent include, but not limited to, aromatic hydrocarbons such as anisole, mesitylene and xylene; ketones such as methyl isobutyl ketone, 1-methyl-2-pyrrolidinone and acetone; ethers such as tetrahydrofuran and isopropyl ether; acetates such as ethyl acetate, butyl acetate and propylene glycol methyl ether acetate; amides such as dimethylacetamide and dimethylformamide; xcex3-butyrolactone; alcohols such as isopropylalcohol, butyl alcohol and octyl alcohol; silicon-based solvents; and mixtures thereof. The solvent should be used in sufficient amount to coat a substrate fully with the siloxane-based resins. Thus, the solvent is added to the siloxane-based resins so that final concentration of the solid matter can be 0.1xcx9c80 wt. %, preferably 5xcx9c30 wt. %.
Non-limiting examples of the method for coating a silicon substrate with the resinous solution containing the siloxane-based resins include spin-coating, dip-coating, spray-coating, flow-coating, screen-printing and so on. Most preferably, the coating is carried out by spin-coating. Following the coating, the solvent is evaporated from the substrate so that a resinous film containing the siloxane-based resins can deposit on the substrate. At this time, the evaporation may be carried out by simple air-drying, or by subjecting the substrate, at the beginning of curing step, to vacuum condition or mild heating (xe2x89xa6100xc2x0 C.).
The resulting coating film may be cured by heating for 1xcx9c150 min at a temperature of 150xcx9c600xc2x0 C., more preferably 200xcx9c450xc2x0 C., so as to provide insoluble film without crack. As used herein, by xe2x80x9cfilm without crackxe2x80x9d is meant a film without any crack observed with an optical microscope at a magnification of 1000X. As used herein, by xe2x80x9cinsoluble filmxe2x80x9d is meant a film which is substantially insoluble in any solvent described as being useful for the coating and deposition of the siloxane-based resins.
The present invention can be more clearly understood with referring to the following examples. It should be understood that the following examples are not intended to restrict the scope of the present invention in any manner.